Internal combustion engine



July 8, 1958 H. TEEGEN INTERNAL COMBUSTION ENGINE Filed Deb. 27, 1955 I7 E M g Mow m B r e a United States Patent INTERNAL COMBUSTION ENGINEHermann Teegen, Bielefeld, Germany, assignor to Diesel Engine Company ofTexas, Houston, Tex, a corporation of Texas Application December 27,1955, Serial No. 555,675

4 Claims. (Cl. 123-43) The invention relates to an internal combustionengine of the self-ignition type compressing an air-fuel mixture, thecompression ratio of said engine being variable, which enables theignition point to be adapted to the respective operating conditions. Inknown engines of this type it has already been proposed to arrangeadjusting members in the cylinder head, which vary the volume of thecombustion chamber. Furthermore, it has also been proposed to separatelyvary said members in their position dependent on the respective cylinderwall temperature, in that outside of the cylinder a thermo-responsiveregulating element is provided, the variations of which beingtransmitted, through a lever arrangement, to the adjusting member whichdetermine the capacity of the combustion chamber. Engines of such kindhave the disadvantage that the control is insufiicient and thatfurthermore a complicated construction of the cylinder head isnecessary.

The invention eliminates the above mentioned deficiencies in thataccording to the invention a control piston is provided opposite thepiston operating in the cylinder, the combustion chamber being formedbetween said two pistons. The control piston, through means .of asealing ring, sealingly bears against the inner walls of the cylinder.Immediately on the upper end of the cylinder, means are provided whichupon variation of the position of the control piston affect the capacityof the combustion chamber, said means being responsive to thetemperature in the combustion chamber.

Due to the arrangement of the thermo-responsive means for the shiftingof the control piston immediately on the upper cylinder end a veryfavorable heat flow is secured. The distance to be bridged for the heattransfer is very short so that the arrangement is very sensitive andeven small temperature changes in the combustion chamber result in animmediate adaption of the chambers capacity.

The thermo-responsive means are preferably formed of outer rings andinner rings which are arranged immediately on the shaft of the controlpiston. The inner rings have a different coefficient of thermalexpansion than the outer rings, i. e. the inner rings and the outerrings consist of different material having different coeflicients ofthermal expansion. t

On the sides facing each other the inner rings and the outer rings areprovided with tapered support surfaces which bear against each other. Anexpansion of the outer rings, caused by a temperature rise results in amore or less deep axial interlocking of the inner rings with the outerrings and thus in an axial shifting of the control piston which bearsagainst the cylinder cover through means of said rings.

In accordance with the invention a sealing ring has been providedbetween the control piston and the cylinder wall which consists of ahelical strip material. On their inner sides the screw-like threads forma tapered seat into which fits the control piston provided with acorrespondingly tapered rim. Through means of the combustion pressure orof a correspondingly arranged spring 2,842,107 Patented July 8, 1958 IIIthe control piston is pressed into the seat of the sealing ring which isexpanded to an extent so that a pressing action against the innercylinder wall and thus a positive sealing action results.

Further details of the invention are specified in the following text andillustrated in the appended drawing, of which Fig. 1 is a longitudinalsectional view through a singlecylinder two-stroke cycle internalcombustion engine in which the air-fuel mixture is compressed in thecrank case and transferred into the cylinder,

Fig. 2 is a sectional view through the lower part of the control piston,on an enlarged scale,

Fig. 3 is a top plan view on the sealing ring employed in combinationwith the control piston.

In the cylinder 1, which on its outer side is provided with wedge-likeribs 2, a piston 3 operates. The piston pin 4 carries the connecting rod5 which on the other side is supported on the crank pin 6.

In the crank case 7 the crank shaft 8 with the crank webs 9 isjournalled in suitable ball or roller bearings. A fly-wheel 10 or apulley, respectively, has been secured to the crank shaft 8 in knownmanner.

The air-fuel mixture is prepared either inside or outside the crank case7. Through channels 12 in the cylinder 1 the air-fuel mixture which hasbeen precompressed in the crank case, is passed to the combustionchamber above the piston 3 in the cylinder 1.

At the upper end the combustion chamber is closed by a control piston13, the outer circumference of which being tapered. On this taperedportion a sealing ring 14 is arranged.

Construction of the seal and its arrangement can be seen clearly fromFigs. 2 and 3. The seal is formed of a helical material strip of alength to form several screwlike threads. The section of the stripmaterial has been selected so that the individual screw threads withtheir fiat surfaces rest closely on each other and that the seal on itsoutside forms a cylindrical body engaging the inner walls of thecylinder 1. The thread portion between the ends of the screw-likethreads are offset so that the seal has a shape as can be seen from Fig.3

The sealing ring formed of the screw-like threads consists of aresilient material. Inside, the sealing ring forms a tapered seat intowhich fits the piston 13. By more or less pressing of the piston 13 intothe seal 14 this is more or less expanded and thus blocked in thecylinder 1. Since the sealing ring 14 forms several screwlike threadswhich leave no gap an absolutely safe sealing action is effected.

In the upper part of the cylinder 1 an enlarged chamber 15 is providedinto which extends the control piston 13 with its shaft in. On the shaft16, in the chamber 15, thermo-responsive means are provided which affecta displacement of the control pistonllS in the cylinder 1. In theembodiment illustrated, these means comprise three inner rings 17, 18,and 19, inovably arranged on the shaft 16. Said three rings are arrangedone after the other with a certain play and provided with tapered.surfaces on their outer circumference. The material of these inner ringshas a low c-oeflicient of thermal expansion.

Between the inner rings 17, 13, or 3.9, respectively, outer rings 20 or21, respectively, are arranged consisting of a material having a highcoeiheient of thermal expansion. On their insides the rings 2i and 21have tapered surfaces corresponding to those on the inner rings 17 or19, respectively, so that the inner and outer rings 17, 2t), 18, 21,.and 19 bear against each other through means of these tapered surfaces.

The ring 1'7 has a collar 22 through means of which it rests on theupper side of the sealing ring 14, whilst the ring 19 has a collar 23and is movably guided in the cyl- 3 inder cover 24. The cover 24 isfixedly bolted to the cylinder through means of bolts 25 and 26 andcloses the upper end of the chamber 15. On the other hand, the cover 24has a cup-shaped indentation 27, which extends into a recess 28 in theshaft 16 of the control piston 13.

In the center of the shaft 16 a bolt 29 is formed on the piston 13 whichpasses through the chamber 27 and which forms a screwed-onspringback-rest 30 for a compression spring 31 outside said chamber 27, saidspring being passed over the bolt 29 and arranged in the chamber 27.

The compression spring tends to pull the control piston 13 against thecylinder cover 24 as soon as the expansible rings 20 and 21 allow forsuch movement, i. e. as soon as the rings 20 and 21 expand due to a risein temperature so that they no longer support the inner rings 17 to 19which then have axial play. On the other hand, the spring 31 presses thecontrol piston 13 into the sealing ring 14 and thus tightly closes theupper end of the cylinder 1.

Both pistons 3 and 13 have a recess 32 and 33, respec- 'tively, on thesides facing each other, whereby the combustion chamber is formed.

Operation of the arrangement is as follows: Both pistons 3 and 13 haveapproached each other so that only a small gap 34 remains between them,and the air-fuel mixture is compressed only in this gap and the chamber32 or 33, respectively. The size of this combustion chamber at first isnot varied, since the control piston 13 is pressed into the sealing ring14 and thus remains in its position in the cylinder 1. As soon as thetemperature rises, the increasing heat is transmitted to the rings 20and 21. The material of these rings has a high coefficient of thermalexpansion which results in a corresponding expansion of the rings. Thusthe rings 17, 18, and 19 lose their axial support. Due to the combustionpressure and the additional action of the spring 31 the control piston13 now can be displaced outwardly for a certain distance which dependsupon the respective temperature, i. e. the combustion chamber capacityis automatically increased and thus adapted to the new operatingconditions. On the other hand, when the temperature decreases, the rings20, 21 are contracted and the inner rings 17, 18, and 19 are pressedapart in axial direction, the control piston 13 is pushed into thecylinder 1 and the capacity of the combustion chamber is reduced.

Iclaim:

1. An internal combustion engine having a cylinder and a piston movablein said cylinder, and including, a control piston in one end of thecylinder, the space between the first piston and the control pistonforming a combustion chamber, means for adjusting the position of thecontrol piston relative to the cylinder to thereby vary the area of thecombustion chamber in accordance with temperature changes, saidlast-named means comprising a plurality of inner rings surrounding thecontrol piston and constructed of a material having a relatively lowcoefficient of expansion, one of said rings engaging a pro jection onthe control piston whereby movement of the rings in a direction parallelto the control piston axis will permit movement of said control pistonrelative to the cylinder, a plurality of outer rings disposedalternately between the inner rings and constructed of a material havinga relatively high co-efiicient of expansion, the bores of the outerrings engaging the outer peripheral surfaces of the inner rings with theengaging surfaces of the rings being inclined, where-by radial expansionand contraction of the outer rings permits the inner rings to move upand down relative to the axis of the cylinder, and a fixed support forconfining the inner rings between said fixed support and the end of thecylinder, whereby as the outer rings expand and contract, the innerrings undergo movement to change the position of the control piston withrespect to the cylinder.

2. An internal combustion engine as set forth in claim 1, together withresilient means constantly acting upon the control piston to urge saidpiston in a direction which will maintain the projection on said controlpiston in contact with one of the inner rings to assure movement ofpiston upon a movement of the inner rings.

3. An internal combustion engine having a cylinder and a main pistonreciprocable therein and including a control piston closing the powerend of said cylinder and slida'ble therein, the area between the mainpiston and the control piston forming a combustion chamber, said controlpiston comprising a main cylindrical body portion and a reduced shaftportion, a series of inner rings surrounding the shaft portion with oneend ring of said series engaging the body portion of the piston, a fixedsupport engaging the other end ring of the series, whereby said ringsare confined between the fixed support and the body portion, and aplurality of outer rings at least partially interposed between andengaging the inner rings, the bore of each outer ring and the surfacesof adjacent engaged inner rings being tapered, whereby expansion andcontraction of the outer rings allows movement of the inner ringsrelative to each other and to the fixed support in a direction upwardlyand downwardly relative to the axis of the cylinder, whereby theposition of the control piston with respect to the main piston maybechanged to thereby vary the area of the combustion chamber, the innerrings being constructed of a material having a lower co-eflicient ofexpansion than the outer rings whereby temperature variations Willresult in adjustments of the control piston.

4. An internal combustion engine as set forth in claim 3, together withan extension on the shaft portion of the control piston extendingthrough the fixed support, and a spring means surrounding the extensionand confined between the fixed support and an enlargement on theextension for constantly urging the control piston in a direction whichurges the series of inner rings in a direction toward the fixed support.

References Cited in the file of this patent UNITED STATES PATENTS1,812,572 Talbot June 30, 1931 1,874,682 Woolson Aug. 30, 1932 FOREIGNPATENTS 495,218 Great Britain Nov. 9, 1938 727,345 Germany Oct. 31, 1942

